DES MOINES, Iowa — In 10 years, an additional 1.8 million trucks will be on the road; in 20 years, for every two trucks today, another one will be added. Already bottlenecks on major highways used by truckers every day are adding millions of dollars to the cost of food, goods, and manufacturing equipment for American consumers. As a result, according to a new report released Thursday, the transportation system that supports the movement of freight across America is facing a crisis.